Preparation of immobilized coating Fenton-like catalyst for high efficient degradation of phenol

In this study, solid acid amorphous Fe₃O₄/SiO₂ ceramic coating decorated with sulfur on Q235 carbon steel as Fenton-like catalyst for phenol degradation was successfully prepared by plasma electrolytic oxidation (PEO) in silicate electrolyte containing Na₂S₂O₈ as sulfur source. The surface morphology and phase composition were characterized by SEM, EDS, XRD and XPS analyses. NH₃-TPD was used to evaluate surface acidity of PEO coating. The results indicated that sulfur decorated amorphous Fe₃O₄/SiO₂ ceramic coatings with porous structure and higher acid strength had the similar pore size and the surface became more and more uneven with the increase of Na₂S₂O₈ in the silicate electrolyte. The Fenton-like catalytic activity of sulfur decorated PEO coatings was also evaluated. In contrast to negligible catalytic activity of sulfur undecorated PEO coating, catalytic activity of sulfur decorated PEO coating was excellent and PEO coating prepared with 3.0 g Na₂S₂O₈ had the highest catalytic activity which could degrade 99% of phenol within 8 min under circumneutral pH. The outstanding performance of sulfur decorated PEO coating was attributed to strong acidic microenvironment and more Fe²⁺ on the surface. The strong acid sites played a key factor in determining catalytic activity of catalyst. In conclusion, rapid phenol removal under circumneutral pH and easier separation endowed it potential application in wastewater treatment. In addition, this strategy of preparing immobilized solid acid coating could provide guidance for designing Fenton-like catalyst with excellent catalytic activity and easier separation.